1997 Infiniti Q45 Engine is difficult to start occasionally

1997 Infinity Q45, mileage 120,000, with new battery. For the past 2 months, the engine is difficult to start occasionally. Sometimes, when I turn on the ignition, it cranks but won't start. After 5 to 10 minutes of sitting with ignition off, then try it again, it will fires and start right up. Car runs great and the engine never die after start. This problem happens only occasionally. Maybe 30%. Thank you.